Heat exchanger

ABSTRACT

A heat exchanger adapted for use in a combination heating and refrigeration system for transferring heat to or from a secondary refrigerant, which includes a plurality of heat exchange tubes closed at one end and opened at the other end with helical corrugations formed in the walls thereof, and a restrictor tube extending into each heat exchange tube and communicating with the closed end of the respective heat exchange tube to receive the primary refrigerant first directed into the respective heat exchange tube, wherein the closed ends of the heat exchange tubes are lower than the open ends thereof and liquid primary refrigerant accumulates in the closed ends of the heat exchange tubes when the exchanger is used in a heating system, such that the rate of flow of primary refrigerant through the heat exchanger is automatically controlled for both refrigeration and heating system operations, and the same amount of primary refrigerant may be used when the system is used for either heating or refrigeration.

United States Patent Park [1 1 3,681,936 451 Aug. 8, 1972 [54] HEATEXCHANGER [72] Inventor: Robert G. Park, Del City, Okla.

[73] Assignee: Oklahoma Manufacturing Company,

Oklahoma City, Okla.

[22] Filed: Oct. 26, 1970 [21] Appl. No.: 83,695

Primary ExaminerWilliam J. Wye Attorney-Dunlap, Laney, Hessin &Dougherty [57] ABSTRACT A heat exchanger adapted for use in acombination heating and refrigeration system for transferring heat to orfrom a secondary refrigerant, which includes a plurality of heatexchange tubes closed at one end and opened at the other end withhelical corrugations formed in the walls thereof, and a restrictor tubeextending into each heat exchange tube and communicating with the closedend of the respective heat exchange tube to receive the primaryrefrigerant first directed into the respective heat exchange tube,wherein the closed ends of the heat exchange tubes are lower than theopen ends thereof and liquid primary refrigerant accumulates in theclosed ends of the heat exchange tubes when the exchanger is used in aheating system, such that the rate of flow of primary refrigerantthrough the heat exchanger is automatically controlled for bothrefrigeration and heating system operations, and the same amount ofprimary refrigerant may be used when the system is used for eitherheating or refrigeration.

3 Claims, 5 Drawing Figures HEAT EXCHANGER BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates generally toimproved heat exchangers. More particularly, but not by way oflimitation, this invention relates to an improved heat exchanger for usein air conditioning systems wherein, the exchanger is utilized totransfer heat to or from a primary refrigerant to a secondaryrefrigerant.

2.Description of the Prior Art The most common form of heat exchangerpreviously constructed for use with secondary refrigerant type airconditioning systems includes a hollow body member having a pair ofplates or bulkheads disposed transversely relative to the elongation ofthe body thereby forming a header or chamber in each end of the hollowbody. A plurality of open-ended tubular members are disposed in thehollow body having each open end in communication with a respective oneof the headers in the heat exchanger and having each end connected withone of the bulkheads. Heat exchangers constructed in this manner weresubject to extreme pressures due to expansion of the secondaryrefrigerant during freezing often resulting in rupture of the heatexchanger.

An improved heat exchanger was disclosed in US. Pat. No. 3,360,036,entitled Heat Exchangers, issued Dec. 26, 1967, to Earl F. Holyfield.The Holyfield heat exchanger includes a plurality of heat exchange tubesclosed at one end and opened at the other end, and a restrictor tubeextending into each heat exchange tube and communicating with the closedend of the respective heat exchange tube. This heat exchanger providedimproved cooling and reliability by providing sub-cooling of the primaryrefrigerant and eliminating the rupture problem resulting from freezingof the secondary refrigerant.

The Holyfield heat exchanger design, though noteworthy, is not asefficient as desired since the heat exchange tubes provide a limitedamount of surface area in contact with the secondary refrigerant for agiven tube length limiting its heat transfer capability.

SUMMARY OF THE INVENTION This invention generally contemplates animproved heat exhanger including: a hollow body having first, second andthird chambers formed therein, and having inlet and outlet openings inthe body in communication with the third chamber; a plurality ofelongated tubes, each having an open end in communication with thesecond chamber, a closed end located in the third chamber, and acontinuous helical corrugation formed in the tube wall throughsubstantially the full length thereof; a plurality of open-ended tubularmembers, each of the members being disposed in a respective one of thetubes and having one open end in communication with the first chamber; afirst conduit connected in fluid communication with the first chamber;and, a second conduit connected in fluid communication with the secondchamber.

One object of the invention is to provide an im proved heat exchanger.

Another object of the invention is to provide an improved heat exchangerfor use in air conditioning systems incorporating secondary refrigerantswherein the heat exchanger will not be damaged should the secondaryrefrigerant freeze.-

One other object of the invention is to provide an im proved heatexchanger that can be used for either heating or cooling a secondaryrefrigerant in an air conditioning system.

Still another object of the invention is to provide an improved heatexchanger providing greater efficiency of operation.

A further object of the invention is to provide an improved heatexchanger requiring no maintenance-during its service life.

Still another object of the invention is to, provide an improved heatexchanger that can be easily and economically constructed.

Theforegoing and additional objects, and advantages of the inventionwillbe more apparent as the following detailed description is read inconjunction with the accompanying drawings wherein like referencecharacters denote like parts inall views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic diagramillustrating the installation of a heat exchanger, constructed inaccordance with the invention, located in. an air conditioning system;

FIG. 2 is an enlarged cross-sectional view of the heat exchanger takensubstantially along the lines 2-2 of FIG. 1;

FIG. 3 is a transverse cross-sectional view taken substantially alonglines3-3 of FIG. 2;

FIG. 4 is a transverse cross-sectional view through the heat exchangerof FIG. 2 taken substantially along the line 4-4 of FIG. 2; and,

FIG. 5 is a fragmentary cross-sectional view more clearly illustratingthe construction of the heat exchanger.

DESCRIPTION OF THE PREFERRED EMBODIMENTS cludes an air conditioning coil14 and a condensing coil 1 6.

One end of the air conditioning coil 14 is connected I with the heatexchanger 12 by an outlet conduit 18. The opposite end of the airconditioning coil 14 is connected with the heat exchanger 12 by an inletconduit 20.

An air trap and bleed 22 is operably disposed in the inlet conduit 20.The air trap 22 is of a conventional construction and is commerciallyavailable from many manufacturers. The purpose of the air trap 22 is toremove air that might be entrained in the secondary refrigerant (notshown) that fills a portion of the heat exchanger 12 in the airconditioning coil 14.

A refrigerant pump 24 is operably connected in the inlet conduit 20between the air trap 22 and the heat exchanger 12. The purpose of therefrigerant pump 24 is to circulate the secondary refrigerant throughthe heat exchanger 12 and through the air conditioning coil 14.

The air conditioning coil 14 is disposed in a casing or duct 26(illustrated in dashed lines in FIG. 1). Some means such as the motordriven fan 28 is provided to force air through the duct 26 and acrossthe air conditioning coil 14. g

The condensing coil 16 is cooled by a motor driven fan 30 and has oneend connected by a conduit 32 with the heat exchanger 12 as will bedescribed more fully in connection with FIG. 2. The other end of thecondensing coil 16 is connected by a conduit 34 with a compressor orrefrigerant pump 36. The refrigerant pump 36 is connected by a conduit38 with the heat exchanger 12 as will also be described more fully inconnection with FIG. 2. The condensing coil 16 and the conduitsassociated therewith are filled with a primary refrigerant (not shown),such as Freon or ammonia.

A valve 40 is operably disposed in the conduit 34 between the condensingcoil 16 and the pump 36. A valve 42 is connected in the conduit 38between the pump 36 and the heat exchanger 12. A branch conduit 44 hasone end connected with the conduit '38 between the valve 42 and the pump36 and the other end connected with the conduit 34 between the valve 40and the condensing coil l6.'A valve 46 is disposed in the branch conduit44. The purpose of the branch conduit 44 and the valve 46 will beexplained more fully hereinafter.

A branch conduit 48 has one end connected with the conduit 34 betweenthe pump 36 and the valve 40 and the other end connected with theconduit 38 between the valve 42 and the heat exchanger 12. A valve 50 isoperably connected in the branch conduit 48 for purposes that willbecome more apparent hereinafter.

FIGS. 2, 3, 4 and illustrate the structure of the heat exchanger 12 indetail. As shown therein, the heat exchanger 12 includes a hollow bodyportion 52 having closed ends 54 and 56.

A perforated plate 58 extends transversely across the hollow body 52(see also FIG. 3). The perforated plate 58 has its peripheral portionconnected in a fluid-tight arrangement with the hollow body 52 to form achamber 60 with the closed end 54 of the heat exchanger 12.

A second perforated plate 62 also extends transversely across the hollowbody 52 (see FIG. 4) in generally parallel spaced relation with theplate 58. The plate 62 has its peripheral portion connected in afluid-tight arrangement with the hollow body 52 forming a chamber 64with the plate 58 and the walls of the hollow body 52. A chamber 66 isformed within the hollow body 52 between the plate 62 and the closed end56 of the hollow body 52.

As may be seen clearly in FIG. 2, the outlet conduit 18 is incommunication with the chamber 66 through an opening 68 formed in thewall of the hollow body 52. Similarly, the inletconduit 20 is incommunication with the chamber 66 through an opening 70 formed in thehollow body 52.

A plurality of elongated tubes 72 are disposed in the hollow body 52.Each tube 72 has an open end 74 extending through an aperture in theperforated plate 62 and connected therewith in fluid-tight relationship.Each tube 72 has a closed end 76 disposed relatively adjacent the closedend 56 of thehollow body 52. Each tube 72 has a continuous helicalcorrugation 78 fonned in the tube wall. Each helical corrugation 78extends from a point on the tube 72 adjacent theconnection between thetube 72 and the perforated plate 62 to a point on the tube 72 adjacentthe closed end 76 and projects radially inwardly from the tube wall. Asmay be clearly seen in FIG. 2, the elongated tubes 72 have the open ends74 disposed in fluid communication with the chamber 64. The majorportions of the tubes 72 are disposed in the chamber 66 in the hollowbody 52 so that they are in contact with the secondary refrigerantfilling the chamber 66.

A plurality of elongated restrictor tubes 80 are also disposed in thehollow body 52. The restrictor tubes 80 each have an open end 82extending through the perforations in the plate 58 and connected withthe plate 58 in fluid-tight relationship. An open end 84 of eachrestrictor tube 80 is disposed in a respective tube 72 relatively nearthe closed end 76 thereof. The restrictor tubes 80 are in intimaterelation with helical corrugations 78 of the respective tubes 72 inwhich they are disposed. The restrictor tubes 80 extend through thechamber 64 and have the open end 82 thereof in fluid communication withthe chamber 60.

The clearance between the outside diameter of the restrictor tubes 80and the inside diameter of the helical corrugations 78 of tubes 72should be as small as possible, consistent with ease of assembly.This-results in the primary refrigerant being caused to follow a spiralpath as it is forced between a restrictor tube 80 and a respectiveelongated tube 72. A typical example of the relative sizes of theseelements would be a clearance of 0.019 inch between a restrictor tube 80having an outside diameter of 0.081 inch and a helical corrugation 78having an inside diameter of 0. l 00 inch. Although a small portion ofthe primary refrigerant will pass through the clearance space betweenthe restrictor tube 80 and the helical corrugation 78, most of theprimary refrigerant will follow the spiral path.

While the various figures of the drawing illustrate the installation ofa relatively small number of tubes 72 and restrictor tubes 80 in theheat exchanger 12, it should be understood that many times the numbershown may be installed in the actual construction of the heat exchanger12. Also, it can be perceived from viewing FIG. 2 that the open ends 82of the restrictor tubes 80 are in communication with the conduit 32through the chamber 60 and that the tubes 72 are in communication withthe conduit 38 through the chamber 64.

Bafile plates 86, 88 and 90 extend generally transversely across thehollow body 52 in spaced parallel relation with the closed end 56thereof and between the conduits l8 and 20. The baffle plates areprovided with a plurality of ports for receiving the conduit 38 and thetubes 72. It should be pointed out that the bafile plates 86, 88 and 90are not connected to the tubes 72 and do not extend entirely across thehollow body 52. The purpose of the baffle plates 86, 88 and 90 is toforce the secondary refrigerant entering the heat exchanger 12 throughthe conduit 20 and the opening 70 to follow a circuitous path throughthe hollow body 52 to the opening 68 and outlet conduit 18. Thus, thesecondary refrigerant is forced into contact with the surface area ofthe greatest number of tubes 72 as it flows through the heat exchanger12.

OPERATION OF THE PREFERRED EMBODIMENTS To utilize the air conditioningsystem for the purpose of cooling, the valves 46 and 50 are closed andthe valves 40 and 42 are opened. With the pump 36 running, the primaryrefrigerant is circulated through the conduit 34 into the condensercoils 16, through the conduit 32 and into the chamber 60 of the heatexchanger 12. The primary refrigerant, as it enters the chamber 60, isin a liquid state. The primary refrigerant flows from the chamber 60into the open ends 82 of the restrictor tubes 80.

As the primary refrigerant flows through the restrictor tubes 80, it ismetered to provide the maximum efficiency of expansion of the liquidrefrigerant as it passes from the open ends 84 of the restrictor tubes80. Upon entering the tubes 72, the primary refrigerant changes into agaseous state and, due to its expansion, becomes extremely cool. Thecooling of the primary refrigerant in the tubes absorbs heat from thesecondary refrigerant in the chamber 66, thereby cooling the secondaryrefrigerant.

As the primary refrigerant flows through the tubes 72, it passes throughthe open ends 74 of the tubes 72 into the chamber 64. From the chamber64, the gaseous primary refrigerant passes through the conduit 38returning to the pump 36.

Simultaneously with the operation of the pump 36, the pump 24 is placedin operation moving the secondary refrigerant through the inlet conduit20, the opening 70 in the hollow body 52 through the chamber 66 aspreviously described. As the secondary refrigerant flows through thechamber 66, it loses its heat to the cooled tubes 72. Therefore, thesecondary refrigerant flowing from the chamber 66 through the opening 68and the outlet conduit 18 to the cooling coil 14 is in a chilledcondition. Air, driven by the fan 28 over the air conditioning coil 14,is cooled to promote the cooling of the area desired.

As can be perceived in FIG. 2, the heat exchanger 12 has an increasedcooling efficiency due to the disposition of the restrictor tubes 80 inthe tubes 72. It can be appreciated therein that as the liquid primaryrefrigerant moves through the restrictor tubes 80 it is precooled" orsub-cooled" due to the expansion of the primary refrigerant as it flowsin a counter-flow direction through the tubes 72 toward the open ends 74thereof. The helical corrugations 78 of the tubes 72 provide acircuitous path for the primary refrigerant to follow as it flows in acounter-flow direction through the tubes 72 toward the open ends 74.This circuitous counter-flow provides more efficient heat transferbetween the tubes 72 and the secondary refrigerant circulating throughthe chamber 66.

When the air conditioning system 10 is to be used as a heat pump, thatis, when it is to be used to heatan area adjacent the air conditioningcoil 14, the valves 40 and 42 are closed and the valves 46 and 50 areopened. With this arrangement of valves, the pump 36 moves the primaryrefrigerant through the branch conduit 48, the valve 50 and into theconduit 38. The primary refrigerant flows through the conduit 38 intothe chamber 64 and then through the open ends 74 of the tubes 72. As theprimary refrigerant flows through the tubes 72, it is condensed due tothe relatively cool secondary refrigerant in the chamber 66. Thecondensed primary refrigerant then passes through the open ends 84 ofthe restrictor tubes 80, flowing therethrough into chamber 60. From thechamber 60, the primary refrigerant flows outwardly through the conduit32 into the condenser coil 16. From the condenser coil 16, therefrigerant flows through the conduit 34, branch conduit 44 and openvalve 46 to the inlet side of the pump 36.

When using the heat exchanger 12 in a heat pump system, the closed end56 thereof should be lowered slightly as shown in FIG. 1. The loweringof the closed end 56 assures that the open ends 84 of the restrictortubes will be immersed in the condensed primary refrigerant in the tubes72 adjacent the closed ends 76 thereof. Thus, the primary refrigerantwhen moved through the restrictor tubes 80 will be in a liquid state.

As the primary refrigerant flows through the tubes 72, the secondaryrefrigerant in the chamber 66 absorbs heat from the primary refrigerantso that the secondary refrigerant flowing through the outlet conduit 18to the air conditioning coil 14 is at an elevated temperature ascompared to the temperature of the secondary refrigerant flowing throughthe inlet conduit 20 into the exchanger 12.

Frequently, heat exchangers utilized in air conditioning systems aresubjected to freezing, particularly when used as a chiller. If thesecondary refrigerant within the chamber 66 freezes, forces are exertedon the structure of the heat exchanger 12 due to the expansion of thefreezing refrigerant. To alleviate the problem of damage to theexchanger 12 when and if such freezing occurs, the tubes 72 aresuspended only at the open end 74 thereof. Also, the restrictor tubes 80are suspended only at the open ends 82 thereof. Thus, the tubes 72 andthe restrictor tubes 80 are free to move under the forces imposed if thesecondary refrigerant in the chamber 66 should freeze.

Also, the thermal expansion of the tubes 72 and 80 under the influenceof changing temperatures in the heat exchanger 12 will not damage theheat exchanger 12 due to the single end suspension of the tubes 72 andthe restrictor tubes 80. In the usual form of constructing heatexchangers, each end of each tube is rigidly supported whereby extremethermal stresses are imposed thereon.

As described in the foregoing detailed description, the heat exchanger12 is arranged so that it can be used without alteration either in anair conditioning system as a heat pump or as a refrigerating device.Also, and as previously mentioned, the heat exchanger 12 avoids thepossibility of damage due to thermal stresses resulting from changes intemperature in the exchanger or from damage due to the freezing of thesecondary refrigerant.

The embodiment described in detail hereinbefore is presented by way ofexample only and it should be understood that many changes andmodifications can be made thereto without departing from the spirit ofthe invention or from the scope of the annexed claims.

What is claimed is:

1. A heat exchanger comprising:

an elongated, hollow body having first and second closed ends and havinginlet and outlet openings therein;

a perforated first plate member disposed in said body adjacent the firstclosed end thereof having a periphery connected in fluid-tightrelationship with said body to form a first chamber in said body;

a perforated second plate member disposed in said body between saidfirst plate member and said second closed end and having a peripheryconnected in fluid-tight relationship with said body to form a secondchamber with said first plate member and a third chamber with the secondclosed end of said body, said third chamber being in communication withsaid inlet and outlet openings;

a first conduit having an open end connected in one of the perforationsin said first plate member with said open end in communication with saidfirst chamber and extending through the second closed end of said bodyto transfer fluid to and from said first chamber; second conduitencircling a portion of said first conduit and having an open end incommunication with said second chamber and connected in one of theperforations in said second plate member, said second conduit alsoextending through the second closed end of said body to transfer fluidto and from said second chamber;

a plurality of tubes disposed in said body, each of said tubes having anopen end connected in a respective perforation in said second platemember, having a closed end thereon disposed in said third chamberadjacent the second closed end of said body, and having a continuoushelical corrugation formed in the tube wall that extends forsubstantially the full length thereof and projects radially inwardlytherefrom;

a plurality of open-ended restrictor tubes disposed in said body, eachof said restrictor tubes having one open end connected in a respectiveperforation in said first plate member in communication with said firstchamber and having the other open end located in and adjacent the closedend of a respective one of said tubes and in intimate relation to thehelical corrugation formed therein; and

a plurality of baffle members located in the third chamber of said bodybetween the inlet and outlet openings whereby fluid flowing therebetweenfollows a circuitous path through said third chamber.

2. A heat exchanger for use in a combination heating and cooling systemwhich includes a compressor circulating a primary refrigerant, and anair conditioning coil through which is circulated a secondaryrefrigerant comprising:

a hollow, elongated body supported with one end slightly lower than theother end thereof having a first chamber in the higher end thereof, athird chamber in the lower end thereof, and a second chamber between thefirst and third chambers, said body further having inlet and outletconnections communicating with the third chamber and adapted forconnection with the air conditioning coil;

a first conduit having one end in communication with said second chamberand having the other end adapted to be connected to the refrigerant com-P a second conduit having one end n communication with said firstchamber and having the other end adapted to be connected with therefrigerant compressor;

a plurality of first tubes supported in said body, each of said tubeshaving an open end in communication with said second chamber, having alower closed end located in said third chamber, and having a continuoushelical corrugation formed in the tube wall that extends forsubstantially the full length thereof and projects radially inwardlytherefrom;

a plurality of open-ended restrictor tubes supported in said body, eachof said restrictor tubes having one open end in communication with saidfirst chamber and having the other open end disposed in a respective oneof said first tubes adjacent the closed end thereof and each of saidrestrictor tubes being in intimate relation to the helical corrugationformed in a respective one of said first tubes, whereby primaryrefrigerant from the compressor either cools or heats the secondaryrefrigerant flowing through said third chamber to the air conditioningcoil depending on whether the primary refrigerant is flowing from saidcompressor into said first conduit or into said second conduit.

3. A heat exchanger as defined in claim 2 wherein:

said first conduit extends through the lower end of the body and thethird chamber into communication with the second chamber, and

said second conduit extends concentrically through the first conduit inthe second chamber into communication with the first chamber.

1. A heat exchanger comprising: an elongated, hollow body having firstand second closed ends and having inlet and outlet openings therein; aperforated first plate member disposed in said body adjacent the firstclosed end thereof having a periphery connected in fluid-tightrelationship with said body to form a first chamber in said body; aperforated second plate member disposed in said body between said firstplate member and said second closed end and having a periphery connectedin fluid-tight relationship with said body to form a second chamber withsaid first plate member and a third chamber with the second closed endof said body, said third chamber being in communication with said inletand outlet openings; a first conduit having an open end connected in oneof the perforations in said first plate member with said open end incommunication with said first chamber and extending through the secondclosed end of said body to transfer fluid to and from said firstchamber; a second conduit encircling a portion of said first conduit andhaving an open end in communication with said second chamber andconnected in one of the perforations in said second plate member, saidsecond conduit also extending through the second closed end of said bodyto transfer fluid to and from said second chamber; a plurality of tubesdisposed in said body, each of said tubes having an open end connectedin a respective perforation in said second plate member, having a closedend thereon disposed in said third chamber adjacent the second closedend of said body, and having a continuous helical corrugation formed inthe tube wall that extends for substantially the full length thereof andprojects radially inwardly therefrom; a plurality of open-endedrestrictor tubes disposed in said body, each of said restrictor tubeshaving one open end connected in a respective perforation in said firstplate member in communication with said first chamber and having theother open end located in and adjacent the closed end of a respectiveone of said tubes and in intimate relation to the helical corrugationformed therein; and a plurality of baffle members located in the thirdchamber of said body between the inlet and outlet openings whereby fluidflowing therebetween follows a circuitous path through said thirdchamber.
 2. A heat exchanger for use in a combination heating andcooling system which includes a compressor circulating a primaryrefrigerant, and an air conditioning coil through which is circulated asecondary refrigerant comprising: a hollow, elongated body supportedwith one end slightly lower than the other end thereof having a firstchamber in the higher end thereof, a third chamber in the lower endthereof, and a second chamber between the first and third chambers, saidbody further having inlet and outlet connections communicating with thethird chamber and adapted for connection with the air conditioning coil;a first conduit having one end in communication with said second chamberand having the other end adapted to be connected to the refrigerantcompressor; a second conduit having one end in communication with saidfirst chamber and having the other end adapted to be connected with therefrigerant compressor; a plurality of first tubes supported in saidbody, each of said tubes having an open end in communication with saidsecond chamber, having a lower closed end located in said third chamber,and having a continuous helical corrugation formed in the tube wall thatextends for substantially the full length thereof and projects radiallyinwardly therefrom; a plurality of open-ended restrictor tubes supportedin said body, each of said restrictor tubes having one open end incommunication with said first chamber and having the other open enddisposed in a respective one of said first tubes adjacent the closed endthereof and each of said restrictor tubes being in intimate relation tothe helical corrugation formed in a respective one of said first tubes,whereby primary refrigerant from the compressor either cools or heatsthe secondary refrigerant flowing through said third chamber to the airconditioning coil depending on whether the primary refrigerant isflowing from said compressor into said first conduit or into said secondconduit.
 3. A heat exchanger as defined in claim 2 wherein: said firstconduit extends through the lower end of the body and the third chamberinto communication with the second chamber, and said second conduitextends concentrically through the first conduit in the second chamberinto communication with the first chamber.